Multivibrator using electroluminescent-photoconductive control elements



3,183,452 UCTIVE 3 Sheets-Sheet 1 Fig. 2. I I

y 1965 E. A. SACK, JR

MULTIVIBRATOR USING ELECTROLUMINESCENT-PHOTOCOND CONTROL ELEMENTSOriginal Filed Dec. 17, 1959 INVENTOR Edgar A. Sock, Jr.

ATTORN w 5 u lHmMI m D H F F T 0 3 E E 6 4 III 7% D Q E V E B rlllL D IiEl. m m 5 1 m m n I151 m M K 1 I 1 v. 1 1 F WITNESSES May 11 1965 E. A.sAcK, JR 3,183,452 MULTIVIBRATOR USINGELECTROLUMINESCENT-PHOTOCONDUCTIVE CONTROL ELEMENTS 3 Sheets-Sheet 2Original Filed Dec. 17, 1959 Fig.7.

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7 I w l w Fig.8.

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3,183,452 PHOTOCONDUCTIVE 3 Sheets-Sheet 3 E. A. SACK, JR

ELECTROLUMINESCEN'I CONTROL ELEMENTS 17, 1959 2 3 O H .l g g g .l a. i FF F & m 1% 4 v m M fi D U E FIIIIL May 11, 1965 MULTIVIBRATOR USINGOriginal Filed Dec.

United States Patent '0 7 Claims. (Cl. 331-107) This invention relatesto control apparatus in general and in particular to controlapparatusutilizing solid state control elements.

This application is a division of application Serial No. 7

860,177, filed December 17, 1959, now abandoned.

The ideal non-mechanical relay has yet to be invented. Such a deviceshould combine certain of the very desirable characteristics of anelectromechanical contactor with the reliability and speed of theall-electric switch. An improved electric relay should possess thefollowing characteristics. Load contacts should constitute a true switchwhose conduction is independent of the polarity, amplitude, frequency,phase, and waveform of the load voltage, current, or power. Loadcontacts should exhibit a very high ratio of closed to openconductivity. In general, closed conductivity should approach infinityand open conductivity should approach zero. Electrical isolation betweenthe load and control terminals should be very high. Load contacts shouldbe capable of handling many times the power required to actuate therelay. The relay should be capable of fast response to the applicationof the control signal. This relay device should have a long life and ahigh reliability. The device should also be small, rugged, and light inweight. For the relay device to find maximum application, it should havethe ability. to respond to a variety of control signals.

The conventional gaseous, vacuum and non-mechanical relays and switchesfall short of meeting all of these specifications. The transistor,thyratron and vacuum tube are not truly bidirectional switches. Ingeneral, in order to use these devices as relays, it is necessary tointroduce a carrier which, when added to the signal to be passed,maintains overall unidirectional polarity. It is often necessary toseparate the signal from the bias before the desired information can bepassed on to some other portion of the circuit. This can lead toconsiderable complication when a direct current level is inherent in thesignal itself and its identity must be retained.

In certain types of relays, such as the magnetic amplifier, the carrieris an alternating rather than a direct potential. Again, the use of sucha switching means immediately introduces the problem of separating thesignal from the carrier.

Although, presently available non-mechanical relays should exhibitsatisfactory ratios of closed to open conductivity, the impedance levelof the device may be inconvenient in certain applications. For example,the vacuum tube is not generally suitable where the switch must controlhigh curre. ts at low voltage levels.

One of the most serious defi iencies of conventional all-electric relaysis the lack of isolation between the load and control terminals.Typically, one load terminal and one control terminal are common whenthe vacuum tube is used as a relay. In a transistor, both of the controlterminals are affected by conditions in the load circuit.

In accordance with the above discussion, an ideal control apparatus oramplifier which regulates an output to a load over a predetermined rangealso has yet to be invented. Such a control apparatus would also need tocom- 7 3,183,452 Patented May 11, 19 65 bine the desirablecharacteristics of the electromechanical and all-electric devicesdetailed hereinbefore.

It is, accordingly, an object of this invention to provide improvedcontrol apparatus.

It is an object of this invention to provide improved control apparatushaving bilateral switching characteristics wherein the load contactsexhibit a high ratio of closed to open conductivity.

A further object of this invention is to provide improved controlapparatus which may function as a switching means.

A still further object of this invention is to provide improved controlapparatus which may function as an amplifier.

It is an object of this invention to provide improved control apparatushaving a long life and requiring no maintenance, that is small, rugged,easy to fabricate, and light in weight.

Other objects of this invention will become apparent from the followingdescription when taken in conjunction with the accompanying drawings. Insaid drawings, for illustrative purposes only, are shown preferredembodiments of the invention.

FIGURE 1 is a diagram illustrating a solid state control elementutilized in this invention;

FIG. 2 is a perspective view of an embodiment of the control elementshown in FIG. 1;

FIG. 3 is a schematic diagram of a basic control or amplifier circuitembodying the teachings of this invention;

FIG. 4 is a schematic diagram of a second embodiment of the teachings ofthis invention;

FIG. 5 is a schematic diagram illustrating a third embodiment of theteachings of this invention;

FIG. 6 is a schematic diagram illustrating a fourth embodiment of theteachings of this invention;

FIG. 7 is a schematic diagram illustrating a fifth embodiment of theteachings of this invention;

FIG. 8 is a schematic diagram illustrating a sixth embodiment of theteachings of this invention;

FIG. 9 is a schematic diagram illustrating a seventh embodiment of theteachings of this invention;

FIG. 10 is a schematic diagram illustrating an eighth embodiment of theteachings of this invention;

FIG. 11 is a schematic diagram illustrating a ninth embodiment of theteachings of this invention;

FIG. 12 is a schematic diagram illustrating a tenth embodiment of theteachings of this invention; and

FIG. 13 is a schematic diagram illustrating an eleventh embodiment ofthe teachings of this invention.

Referring to FIG. 1, there is illustrated the solid state controlelement used in the embodiments of this invention. Element E is anelectroradiative transducer. The application of a potential to a pair ofcontrol terminals 10 and Il, causing a passage of current through thiselement E, generates a radiation which is guided to or focused onelement D. Element D is radiation-sensitive. The radiation from elementE causes the electrical impedance characteristics of the element D tovary at a pair of load terminals 12 and 13. i

The exact geometry of the configuration illustrated in FIG. 1 willdepend upon the materials to be used, the desired impedance levels inthe load and control circuits, the power to be handled bytheradiation-sensitive element D, etc. If the areas of the element E andthe element D are significantly different, a-lens may be included inorder to optimize the transfer of the radiant energy. Although.

vided into two types or modes of .operation.

modulated carrier.

Referring to FIG. 2, there is illustrated a perspective view of anembodiment of the solid state control element illustrated in FIG. 1. Theelement E, in this case, may be an electroluminescent cell,alternating-current or direct-current, while the element D may be aphotoconductor. The layer T between the electroluminescent cell E andthe photoconductor D may be any suitable transparent insulator. Thedevice is to be encapsulated in a container which is impervious toambient radiation which would affect the performance of element D andwhich has either terminals or leads on the encapsulated device for thecontrol terminals and 11 and the load terminals 12 and 13.

To facilitate the description of the following embodiments, theelectroradiative element E will be divided into two types. Type I willbe an element in which the instantaneous intensity of the outputradiation may beconsidered as varying with the instantaneous amplitudeof the applied potential or current. Cadmium, sulfide or silicon carbidecrystals are examples of Type I electroluminescent emitters. Adirect-current electroluminescent cell would be classified as Type I.Type II will be an element in which the average intensity of the outputradiation may be considered as varying with the amplitude of an appliedcarrier potential. Zinc sulfide, copper activated, is an example of TypeII electroluminescent emitter. An alternating-current electroluminescentmaterial is here classified as Type II.

The radiation-sensitive transducers may also be di- In Type A, theelectric characteristics are assumed to vary with the instantaneousintensity of the incident radiation. The electrical characteristics of aType B material, however, follow the average amplitude of the incidentradiation over some time interval. Cadmium sulfide, lead sulfide,cadmium selenide and zinc tellanide are examples of Type A radiationdetectors. The same materials as Type A may be used for Type B exceptinput radiation varies too fast for the detectors to followinstantaneously and, instead responds to average radiation.

Referring to FIG. 3, there is illustrated a schematic diagram of a basiccontrol or amplifier circuit, utilizing the solid state control elementhereinbefore discussed, embodying the teachings of this invention. InFIG. 3 the solid state element 20 is illustrated symbolically with Esymbolizing an electroradiative transducer or emitter and D symbolizinga radiation sensitive transducer or detector. The emitter E of thecontrol element 20 is connected in series circuit relationship betweenthe terminals 10 and 11. The detector D is connected in series circuitrelationship with a load and a pair of terminals and 46.

In operation, if the emitter E is Type I and the detector D is Type A,then the signal to be applied to the terminals 10 and 11 is adirect-current. The power supply to be connected to the terminals 45 and46 may be either an alternating or a direct-current. The magnitude ofthe direct-current control signal applied to the terminals 10 and 11varies the flow of power from the terminals 45 and 46 through the load30. An increase in the magnitude of the signal applied to the terminals10 and 11 increases the amount of radiation from the emitter E of thecontrol element 20. This radiation varies the impedance of the detectorD of the control element 20 allowing more power to flow from theterminals 45 and 46 through the load 30. If the detector D is aphotoconductive cell, the resistance will be lowered. Other types ofdetectors will vary their internal impedance in accordance with theamount of radiation received.

If the emitter E of the control element 20 is Type II the signal appliedto the terminals 10 and 11 is a The flow of power to the load 30 nowvaries directly with the amplitude of the applied carrier to theterminals 10 and 11. Again, the power 4 supplied to the load 30 from theterminals 45 and 46 may be either alternating-current or direct-current.

If so desired, a bias potential or current may be applied to theterminals 14 and 15 connected in parallel with the signal terminals 10and 11 to bias the emitter E to some level of radiation or excitation.With proper coupling of the input signal circuit to the terminals 10 and11, the bias potential or current may be applied to the emitter E inseries with the emitter E and between the terminals 10 and 11. Whetherthe bias is alternating or direct-current voltage depends upon Whetherthe emitter E is Type II or'Type I, respectively.

It is to be noted that the apparatus illustrated in FIG. 3 may be usedin two distinct modes. In a switching mode the detector D of the controlelement 20 is either conducting or non-conducting. That is, theelectrical input signal when applied to the terminals 10 and 11 will beof sufficient magnitude to excitethe emitter E to radiate or switch thedetector D into full conduction. The switching mode is analogous to theoperation of a true relay or switch. In a control mode the detector Dwill vary its impedance in a substantially continuous manner inaccordance with the magnitude of the electrical input signal applied tothe terminals 10. and 11 which excites the emitter E. The control modeis analogous to the operation of an amplifier.

Referring to FIG. 4 there is illustrated a schematic diagram of twocascaded Type I-A control element amplifiers embodying the teachings ofthis invention. 'In general, the apparatus illustrated in FIG. 4comprises means for applying an input signal at the terminals 10 and 11,an input stage control element 20 having an emitter E and a detector D,a coupling resistor 41, an output stage control element 40 having anemitter E and a detector D, means for connecting a load 30 and means forapplying a direct-current supply.

The emitter E of the control element 20 is connected in series circuitrelationship between the terminals 10 and 11. The detector D of thecontrol element 20 is connected in series circuit relation between aterminal 21 and a terminal 22. The coupling resistor 41 and the emitterE of the control element 40 are connected in parallel circuitrelationship between .the terminal 22 and ground. The detector D of thecontrol element 40 is connected in series circuit relationship with aload 30 between the terminal 21 and ground. A suitable source of directcurrent is to be connected, with polarity as shown, between the terminal21 and ground.

The operation of each of the control elements 20 and 40 is similar tothe operation of the control element 20 in FIG. 3. Upon application of adirect current signal to the terminals 10 and 11 the emitter Eof thecontrol element 20 starts emitting radiation to the detector D of thecontrol element 20. Upon receipt of radiation the resistance of thedetector D of the control element 20 will fall, allowing a current flowfrom the terminal 21 through the detector D of the control element 20,the terminal 22 and the resistor 41 to ground. A voltage drop, withpolarity as shown, across the resistor 41 will cause the emitter E ofthe control element 40 to start radiating the detector D of the controlelement 40. The resistance of the detector D of the control element 40falls, allowing current flow from the terminal 21 through the detector Dof the control element 40 and the load 30 to ground.

Several stages of control elements may be connected in theabove-described manner utilizing a common directcurrent source supply asshown in FIG. 4, although separate direct current supplies may be used.

Referring to FIG. 5, there is illustrated a schematic diagram of twocascaded Type IIB control elements, embodying the teachings of thisinvention in which like elements of the FIGS. 4 and 5 have been giventhe same reference characters. The main distinction between theapparatus illustrated in FIGS. 4 and 5 is that in FIG. 5

the coupling transformer 50 has been substituted for the couplingresistor 41 of FIG. 4 since a carrier is to be applied between theterminal 21 and ground instead of a suitable source of direct-current.The detector D of the control element 29 is now in series relationshipwith the primary winding 51 of the transformer 5t between the terminal21 and ground. The emitter E of the control element 40 is now in seriescircuit relationship with the secondary winding 52 of the transformer50.

In operation an alternating-current signal is to be applied to theterminals 19 and 11 causing the emitter E of the control element 2 3 toemit radiation to the detector D or" the control element 2%. Theresistance of the detector D of the control element 2% will fall with anincrease in the amplitude of the carrier signal applied to the terminalsand 11 and will allow current fiow from the terminal 21 through thedetector D of the control element and the primary winding 51 of thetransformer St] to ground and a first half-cycle, and in the reversedirection on the next half-cycle, of the carrier connected between theterminal 21 and ground. A voltage will be induced in the secondarywinding 52 of the transformer 50 which causes the emitter E of thecontrol element 49 to emit radiation to the detector D of the controlelement 20 allowing a current flow from the terminal 21 through thedetector D of the control element 40 and the load 39 to ground. On thenext half-cycle of the carrier connected between the terminal 21 andground current will flow in a reverse direction through the load 3% andthe detector D of the control element 443 to the terminal 21. A numberof stages of the Type ILB control elements may be cascaded in the mannershown in FIG. 5. The various stages of FIG. 5 may also be driven fromseparate carrier supplied instead of the one connected between theterminal 21 and ground.

In cascading the Type l-A, Type II-A, Type LB and Type IIB there are anumber of different coupling arrangements that may be used betweenstages depending upon the type of signal received from the precedingstage. By proper design, coupling networks between stages may beeliminated entirely. The cascaded control elements may be used in eitherthe switching or amplifying modes as described hercinbefore.

If bias is desired in any or all of the plurality of stages of theapparatus illustrated in FIGS. 4 and 5, it may be applied, as describedfor the apparatus illustrated in FIG. 3, in the emitter circuit of anystage.

Referring to FIG. 6, there is illustrated a schematic diagram of afeedback oscillator, using a Type LA control element, embodying theteachings of this invention. Since the amplifiers hereinbefore discussedcan deliver a power gain, the output of a single stage can be fed backinto the input of that stage with such a phase and amplitude as toresult in oscillation. In the apparatus iilustrated in FIG. 6, anemitter E or" a control element 6%) is connected in series circuitrelationship with a first winding 71 of a transformer 79 and a firstsource of direct current 61. A detector D of the control element on isconnected in series circuit relationship with a second winding 72 of thesaturating transformer 70 and a second direct current source 62.

When the direct current sources 61 and 62 are first connected to thecircuit of FIG. 6, there will be no potential applied to the emitter Eof the control element 63 until the saturable reactor 79 saturates. Thatis, the winding '71 of the saturable reactor 73 supports the voltageapplied by the direct current source 61 until the saturable reactor 76reaches negative saturation. Upon saturation of the saturable reactor75), the winding '71 approximates virtuallyzero impedance and the entirepotential of the direct current source 61 is now across the emitter E ofthe control element at The emitter E starts to radiate the detector D ofthe control element 69. The resistance of the detector D of the controlelement 6%) starts to fall and the winding 72 of the saturable 6 reactor70 now supports the voltage supplied by the direct source 62.

During the period that the saturable reactor 70 is being driven topositive saturation by the ampere-turns applied by the direct currentsource 62, there is a voltage induced in the winding 71 of the saturablereactor 70 of such polarity as to said the direct current source 61 inapplying a potential to the emitter E of the control element 60. Thus,the emitter E is now supplying more radiation to the detector D of thecontrol element 6% and further lowering the resistance of the detectorD. Upon positive saturation of the saturable reactor 79, the fieldprovided by the induced voltage in winding 71 of the saturable reactor70 collapses, opposing the potential provided by the'direct currentsource 61. This reduces the potential applied to the emitter E and thusthe radiation supplied to the detector D. Therefore, when the resistanceof the detector D goes up, current in the winding 72 will startdecreasing and the field in the winding 72 starts collapsing whichinduces a current in winding '71 further opposing the direct currentsource 61. This again reduces the radiation to D driving its re sistancehigher and the action follows through until the emitter E stopsradiating to the detector D and the cycle starts all over again.

The apparatus illustrated in FIG. 6 will also oscillate if transformer76 is a simple transformer and not a saturable reactor. Since the solidstate control element 6% acts as an amplifier then if the output isconnected to the input in a regenerative manner, the device willoscillate. The direct current source 61 must be sufficiently large thatthe voltage across the emitter E of the control element 6% remainsunidirectional.

Assume that the potential across the emitter E is increasing. Since thecontrol element 60 is an amplifier the voltage across the winding 72will be increasing and be larger in magnitude than the potential acrossthe emitterE. Therefore, the induced voltage appearing across thewinding 71 will reinforce the original increasing potential across theemitter E. This reinforcement will continue until the voltage acrosswinding 72 reaches the value of the. direct current source 62 or untilsome component in the circuit tends to saturate. The transformer 74?cannot sustain a non-changing potential across the winding 71. Hence thevoltage across the winding 71 drops, the potential across the emitter Edrops and the direction of oscillation reverses.

Referring to FIG. 7, there is illustrated a schematic diagram of anotherform of-an oscillator, utilizing the solid state control element 8%,embodying the teachings of this invention. A direct current source 82with pa larity as shown is connected between the emitter E and thedetector D of the control element 86 to the terminals 97 and 99,respectively. An adjustable tapped resistor 91 is connected between theterminals 97 and 9?. A resistor $3, terminal 96 and a coupling capacitor94 are connected in series circuit relationship between the terminal 97and a terminal 98 on the other end of the emitter E of the controlelement 80. The tap of the adjustable tapped resistor 91 is connected tothe terminal W). The detector D of the control element 89 is connectedin series circuit relationship between the terminals 99 and d6. 7

The tapped resistor 91 is set so that the potential across the emitter Eremains unidirectional. Assume that the potential across the emitter Eis'increasing. Since the control element 89 is an amplifier then thevoltage across the resistor 93 is increasing and may be larger than thepotential across the emitter E.

The increase in voltage across the resistor 93 is coupled over to theemitter E by the capacitor 94 and reinforces the original increasingpotential across the emitter E. This reinforcement action continuesuntil the voltage across the resistor 93 reaches the value of the directcurrent source 82 or until some component in thecircuit 71 tends tosaturate. The capacitor 94 cannot sustain a non-changing potentialacross the emitter E which is greater than the voltage across the tappedresistor 91, and, therefore, the potential across the emitter E startsto fall.

The fall in potential across the emitter E is reinforced through thecoupling capacitor 94 by the resulting fall in voltage acrosstheresistor 93 until the potential across the emitter E tends to gonegative. The potential across the emitter E cannot remain at zero sincethe voltage applied to the emitter E from the tapped resistor 91 willtend to pull it back up. The cycle then repeats.

Referring to FIG. 8, there is illustrated a schematic diagram of abistable multivibrator, utilizing the solid state control elements 110and 129, embodying the teachings of this invention. A resistor 111, aterminal 112, and the detector D of the first control element 110 areconnected in parallel circuit relationship with a resistor 121, aterminal 122,and the detector D of the second control element 120between a terminal 116 and ground. An emitter E of the control element110 is connected between the terminal 122 and ground. An emitter E ofcontrol element 120 is connected by the terminal 112 and ground. Adirect-current source 115, with polarity as shown, is connected betweenthe terminal 116 and ground.

Assume that the emitter Eof the control element 119 is not radiating.Then the detector D of the control element 116 has a high resistance sothat nearly all of the potential supplied by the direct-current source115 appears across the emitter E of the control element 126 from theterminal 116 and through the resistor 111. This potential causes theemitter E of the control element 120 to radiate and also keeps itradiating.

As long as the emitter E of the control element 120 is radiating, thedetector D of the control element 120 is conducting and the voltage dropacross the detector D of the control element 120 will be very small.Since the emitter E of the control element 110 is connected across thedetector D of the control element 120 and ground, the voltage across theemitter E of the control element 110 will be small and the emitter Ewill not radiate the detector D of the control element 110.

If a negative trigger pulse is injected at the terminal 112 the voltageacross the emitter E of the control element 120 will drop therebyreducing the radiation to the detector D of the element 120. Theresistance of the detector, D of the control element 120 will rise andthus cause the voltage drop across the detector D of the control element128 to rise. Since the emitter E of the control element 119 is connectedacross the detector D of the control element 120, the voltage across theemitter E of the control element 116 will also rise causing it toirradiate the detector D of the control element 110. The resistance ofthe detector D of the control element 110 will decrease, the detector Dof the control element 110 will start to conduct and the voltage dropacross the detector D of the control element 120 will fall. This fall inthe voltage drop across the detector D of the control element 11b inturn reduces the voltage supply to emitter E of the control element 120,thereby reducing the radiation to detector D of the control element 129.This, in turn, raises the voltage across the emitter E of the controlelement 116.

As can be seen, the action will continue until the circuit illustratedin FIG. 8 assumes the alternate stable state of the detector D of thecontrol element 11!) conducting and the detector D of the controlelement 120 non-conducting. A negative trigger pulse of the propermagnitude injected at the terminal 122 will cause the apparatusillustrated in FIG. 8 to revert to its original state. A positivetrigger pulse maybe used for triggering it it is applied to the emitterE of the non-conducting control element. The positive trigger pulse willthen change the circuit to its alternate stable state.

' control element 130.

It is to be noted that the apparatus illustrated in FIG. 8 may also betriggered optically. For example, light or radiation valve meansoptically disposed between the emitter E and the detector D of eachcontrol element may be used to reduce the effect of the emitter E inradiating the detector D and the circuit will change to its alternatestable state.

Referring to PEG. 9 there is illustrated a schematic diagram of across-coupled multivibrator, utilizing first and second solid statecontrol elements and 140, embodying the teachings of this invention.

A resistor 131, a terminal 123, and a detector D of the control element13% are connected in parallel circuit relationship with a resistor 141,a terminal 144, and the detector D of the control element 149 between aterminal 13? and ground. A coupling capacitor 142, a terminal 145, andan emitter E of the control element 138 are connected in series circuitrelationship between the terminal 144- and ground. A coupling capacitor132, a terminal 134 and an emitter E of the control element 140 areconnected in series circuit relationship between the terminal 129 andground. A resistor 143 is connected in series circuit relationshipbetween the terminal 14-5 and a tap 138 of an adjustable tapped resistoror potentiometer 137. A resistor 133 is connected in series circuitrelationship between the terminal 134 and the tap 138 of the adjustabletapped resistor 137. The tapped adjustable resistor 137 and the directcurrent source 135, with polarity as shown, are connected in parallelcircuit relationship between the terminal 139 and ground.

To explain the operation of the apparatus illustrated in FIG. 9, we willassume that the excitation, or the potential across the emitter E of thecontrol element 130 is decreasing. Therefore, the voltage across thedetector D of the control element 130 is increasing towards thepotential of the direct current source connected to the terminal 139.Because of the effect of the capacitor 132, when the potential risesacross the detector D of the control element 139, the potential willalso rise across the emitter E of the control element 140. Thus, thevoltage across the detector D of the control element 140 decreases andthis voltage decrease is reflected across the emitter E of the controlelement 130, by the action of the capacitor 142, which reinforces thedecreasing action of the capacitor 142, which reinforces the decreasingaction of the voltage across the emitter E of the Finally, the voltageacross the detector D of the control element 130 will reach thepotential of the direct current source 135 and can increase no further.Thus the voltage across the emitter E of the control element 140 Willstart to decrease causing the voltage across the detector D of thecontrol element 140 to increase and, through the action of the capacitor142, will start to increase the voltage across the emitter E of thecontrol element 139. The voltage across the detector D of the controlelement 130 will now start to decrease and this'will be reflected acrossthe emitter E of the control element 146 by the action of the capacitor132, lowering the potential across the emitter E of the control element140 further. The voltage across the detector D of the control element130 will eventually rise to the potential of the direct current supply135 at which time the cycle is completed and starts again.

Referring to FIG. 10, there is illustrated a schematic diagram of apower modulator, utilizing a Type I-A control element 150, embodying theteachings of this invention. An emitter E'of a control element 15%) isconnected in series circuit relationship between a pair of terminals 151and 152. A detector D of the control element is connected in seriescircuit relationship with a load and a means for applying a carrier 154.From the description hereinbefore of the Type I-A control element, itmay be seen that the carrier 154 amplitude across the load 1.55 willvary in accordance with the direct current signal input applied to theter- *9 minals 151 and 152. If so desired, a direct-current bias source156 may be inserted in series in the input circuit to establish adesired amplitude level.

Referring to FIG. 11, there is shown a schematic diagram of ademodulator circuitutilizing a Type ILB control element 160. An emitterE of the control element 169 is connected in series circuit relationshipbetween a pair of terminals 161 and 162. A detector D or" the controlelement 169 is connected in series circuit relationship with aload 165and a direct current source 164. As would be expected from thedescription of a Type II.B control element hereinbefore, the potentialacross the load 165 will vary in accordance with the amplitude of amodulated carrier signal applied at the input terminals 161 and 162.

Referring to FIG. 12, there is showna control element .170 having twoType I electroluminescent cells E and E radiating a single Type Aphotoconductor. The Type II emitter may be used in combination with theType A or B detectors in a similar embodiment. The control element 170is illustrated in a schematic diagram of a summation amplifier embodyingthe teachings of the invention.

The emitter E of the control element 170 is connected in series circuitrelationship between the terminals 171 and 172. The emitter E of thecontrol element 170 is connected between the terminals 175 and 177. Thedetector D of the control element 170 is connected in series circuitrelationship with the load 175 and a direct current source 174. Theintensity of the radiation from the emitters E and E falling upondetector D is proportional to the sum of the outputs from each of theelectroluminescent cells. It is possible to select parameters so thatthe output signal across the load 175 is proportional to the sum of theinput signals applied to the input terminals 171, 172 and 176, 177. Inthis manner a plurality of emitters may radiate one detector or aplurality of detectors may be radiated by one emitter per forming afunction analogous to multipole-multicoil relays.

Referring to FIG. 13, there is illustrated a schematic diagram of agating amplifier embodying the teachings of this invention. A radiationvalve 139 has been added between an emitter E and a detector D of acontrol element 180. The emitter E is connected between a pair ofterminals 181 and 182. The radiation valve 139 is connected between apair of terminals 186 and 187. The detector D of the control element 180is connected in series circuit relationship with a direct current source184 and a load 185. The radiation valve 189 may be a crystal withvoltage variable birefringence placed between polarizing sheets, or maybe any element with radiation attenuation characteristics that arechanged by an electrical signal.

Without the radiation valve 189 the operation of the apparatusillustrated in FIG. 13 is the same as the operation of the apparatusillustrated in FIG. 3. However, the addition of the radiation valvegives us a means of gating the amplifier, that is, an input may bepresent in the terminals 181 and 182, but will not change the resistanceof the detector D in the load circuit until an input appears at theterminals 186 and 187 and causes the radiation valve to be operative topass radiation emitted by the emitter E of the control element 180.

Since the gain of the amplifier illustrated in FIG. 13 may be varied bythe signal applied to the terminals 18% and 187 of the radiation valve,the circuit may be adapted to provide an output which is a product oftwo input signals.

The control elements and control apparatus illustrated in the foregoingembodiments have exhibited the following advantages. There is anexcellent electrical isolation between the load and control terminals.Complete control of load circuit conditions is very good since theconductivity of the detectors in the load circuit may be varied by afactor of 10 or more. This manner of con- 10 .trol exhibits a sharpcutoff characteristic. This method of control is suitable for handlinguseful amounts of power at practical impedance levels. The structure issmall, rugged, easy to fabricate, and light in weight. Control devicesof this sort'should have a long life and require no maintenance.

The control device may be manufactured as a packagedencapsulated unit asa general circuit component in a Wide variety of sizes and having a widevariety of applications.

In conclusion, it is pointed out that while the illustrated examplesconstitute practical embodiments of my invention, I do not limit myselfto the, exact details shown, since modifications of the same may bevaried without departing from thespirit of this invention.

I claim as my invention: a H

1. In a controlapparatus, in combination, first and secondcontrolelements, each said control element comprisingan-electroradiative transducer having control terminals and a radiationsensitive device havingload ter- Ininals, means for connecting a directcurrent source to a parallel circuit having two branches, each of saidbranches comprising said radiation sensitive device of one of saidcontrol elements and a resistive means, said electroradiative transducerof said first control element being connected across said radiationsensitive device of said second control element, said electroradiativetransducer of said second control element being connected across saidradiation sensitive device of said first control element, and means forapplying an electrical pulse to each said parallel branch, whereby oneof said radiation sensitive devices of one of said control elements isstopped from conducting and said radiation sensitive device of the othersaid control element starts conducting.

' 2. In a control apparatus, in combination, first and second controlelements, each said control element comprising an electroradiativetransducer having control terminals and a radiation sensitive devicehaving load terminals, means for connecting a direct current source to aparallel circuit having two branches, each of said branches comprisingsaid radiation sensitive device of one of said control elements and aresistive means, said electroradiative transducer of said first controlelement being connected across said radiation sensitive device of saidsecond control element, said electroradiative transducer of said secondcontrol element being connected across said radiation sensitive deviceof said first control element, and means for applying an electricalpulse to the junction of said radiation sensitive device and saidresistive means of each said parallel branch whereby one of saidradiation sensitive devices of one of said control elements is stoppedfrom conducting and said radiation sensitive device of the other saidcontrol element starts conducting.

3. In a control apparatus, in combination, first and second controlelements, each said control element comprising an electroluminescentcell having control terminals and a photoconductor having loadterminals, means for connecting a direct current source to a parallelcircuit having two branches, each of said branches comprising saidelectroluminescent cell of one of said control elements and a resistivemeans, said electroluminescent cell of said first control element beingconnected across said photoconductor of said second control element,said electroluminescent cell of said second control element beingconnected across said photoconductor of said first control element, andmeans for applying an electrical pulse to the junction of saidphotoconductor and said resistive means of each said parallel branchwhereby one of said photoconductor of one of said control elements isstopped from conducting and said photoconductor of the other saidcontrol element starts conducting.

4. In a control apparatus, in combination, first and second controlelements, each said control element com prising an electroradiativetransducer having control terminals and a radiation sensitive devicehaving load terminals, meansfor connecting a direct current source to aparallel circuit having two branches, each of said branches comprisingsaid radiation sensitive device of one of said control elements and aresistive means, circuit means connecting a coupling capacitor and saidelectroradiative transducer of each said control element across saidradiation sensitive device of the other said control element, and meansfor applying a. direct current voltage to said electroradiativetransducer of said first and second control elements.

5. In a control apparatus, in combination, first and second controlelements, each said control element comprising an electroradiativetransducer having control terminals and a radiation sensitive devicehaving load terminals, means for connecting a direct current source to aparallel 'circuit having two branches, each of said branches comprisingsaid radiation sensitive device of one of said control elements and aresistive means, circuit means connecting a coupling capacitor and saidelectroradiative transducer of each ,said control element across saidradiation sensitive device of the other said control element, andpotentiometer means for applying a direct current voltage throughcurrent limiting means to said electroradiative transducers of saidfirst and second control elements.

6. In a control apparatus, in combination, first and second controlelements, each said control element comprising an electroradiativetransducer having control terminals and a radiation sensitive devicehaving load terminals, means for connecting a direct current source to aparallel circuit having two branches, each of said branches comprisingsaid radiationrsensitive device of one of said control elements and aresistive means; and switching means operatively connected to eachparallel branch to permit the radiation sensitive device one of saidcontrol elements to conduct While prohibiting the radiation sensitivedevice of the other of said control elements from conducting.

7. In a control apparatus, in combination, first and second controlelements, each said control element comprising an electroluminescentcell having control terminals and a photoconductor having loadterminals, means for connecting a direct current source to a parallelcircuit having two branches, each of said branches comprising saidphotoconductor of one of said control elements and a resistive means,circuit means connecting a coupling capacitor and saidelectroluminescent cell of each said control element across saidphotoconductor of the other said control element, and potentiometermeans for applying a direct current voltage through current limitingmeans to said electroluminescent cell of said first and second controlelements.

References Cited by the Examiner UNITED STATES PATENTS 2,904,696 9/59Elliott et a1. 30788.5 2,947,874 8/60 Tomlinson 307-88.5 2,975,290 3/61Spitzer 331-107 OTHER REFERENCES Journal British I.R.E., March 1957,pages 141-154, Principles of the Light-Amplifier and Allied Devices,Tomlinson (only pages 149, 150 relied upon).

ROY LAKE, Primary Examiner.

4. IN A CONTROL APPARATUS, IN COMBINATION, FIRST AND SECOND CONTROL ELEMENTS, EACH SAID CONTROL ELEMENT COMPRISING AN ELECTRORADIATIVE TRANSDUCER HAVING CONTROL TERMINALS AND A RADIATION SENSITIVE DEVICE HAVING LOAD TERMINALS, MEANS FOR CONNECTING A DIRECT CURRENT SOURCE TO A PARALLEL CIRCUIT HAVING TWO BRANCHES, EACH OF SAID BRANCHES COMPRISING SAID RADIATION SENSITIVE DEVICE OF ONE OF SAID CONTROL ELEMENTS AND A RESISTIVE MEANS, CIRCUIT MEANS 